Planning a trip to San Francisco in September? You are in luck! The weather is generally good, with an average maximum temperature of +75°F and approximately 9 sunny days. Just be prepared for some rain, as there are usually around 2 rainy days and 4 mm of precipitation. Expect good weather and pack accordingly to enjoy the outdoors. Search flightsin one click on Avionero.
Good to know:
September is usually the hottest month of the year in San Francisco;
Average weather
☀️
+75°F
Avg. max. temperature
+48°F
Min.
+99°F
Max.
4 mm
Total precipitation
81%
Avg. humidity
2 m/s
Avg. wind
9 ☀️
Sunny Days
19 ⛅️
Cloudy
2 🌦
Rainy
Our opinion: San Francisco has good weather in September.
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Average temperature in San Francisco in September
Here are the expected maximum, average and minimum temperatures in San Francisco for September based on the historical data.
Last Year
Historical Data
Going from a maximum of +77°F during the day to a minimum of +55°F during the night, the temperature in September averages around +72°F.
The average maximum temperature goes down 8% by the end of the month, compared with the beginning of the month, from +70°F to +68°F.
Is San Francisco warm or cold in September?
San Francisco is typically warm in September.
Maximum temperatures go up compared to the previous month from +75°F to +75°F. The minimum temperature also goes up from +57°F to +57°F.
It’s generally warm, but pack a long-sleeve shirt for evenings.
September is the hottest month in San Francisco, here is the comparison with other months:
Water temperature in San Francisco in September
Water in San Francisco in September is Cold. It varies from +55°F to +59°F, with an average of +57°F.The air temperature averaging +75°F is higher than the water temperature.
The water temperature in September is one of the warmest of the entire year:
The warmest water temperatures in San Francisco are reached in September, when the average sea temperature rises to +57°F. The coldest water temperatures are in June, with an average of +52°F.
Can you swim in San Francisco in September?
We would not recommend swimming in San Francisco in September, the water is very cold (+57°F on average). Consider swimming only if you are an experienced cold-water swimmer with proper gear.
🦭
Cold
Below +61°F
🏄♂️
Fresh
61°F - 70°F
🏊
Comfortable
70°F - 77°F
👙
Warm
77°F - 82°F
🔥
Very warm
+82°C and up
You will need a full-body wetsuit, cap, gloves, a warm change of clothes, and a hot drink ready for after your swim.
Climate in San Francisco in September
San Francisco weather looks like this, on average, in September and the surrounding months.
August
September
October
Avg. temperature
+75°F
+75°F
+72°F
Min. temperature
+50°F
+48°F
+43°F
Max. temperature
+93°F
+99°F
+95°F
Rainfall
1 mm
4 mm
29 mm
Wind
2 m/s
2 m/s
2 m/s
Avg. water temperature
+56°F
+57°F
+57°F
Humidity
83%
81%
79%
Air pressure
1013 HPa
1012 HPa
1014 HPa
Sunny days
6
9
10
Cloudy days
24
19
16
Rainy days
0
2
5
Snowy days
0
0
0
September weather is still as good as in August.The temperature levels stay the same in the area of +75°F for average maximum temperature during the day.Prepare for more rain. Average rainfall goes from 1 mm to 4 mm.It feels drier, as humidity decreases from 83% to 81%.The average wind speed doesn’t change much during September, staying around 2 m/s.The good news is there are likely to be more sunny days in September, from 6 to 9.
October brings much the same weather, it remains good.
Wind speed in San Francisco in September based on historical data.
Last Year
Historical Data
The average wind speed is 1 m/s getting up to 2 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in San Francisco is gradually decreasing during September, going from 2 m/s to 1 m/s over the course of the month.
Rain
Amount of rainfall in mm during September in San Francisco based on historical data.
Last Year
Historical Data
Typically, there is a 10% chance of rain on an average day in September, with total rainfall of approximately 4 mm. The maximum amount of rainfall per day is around 2 mm, which is considered light rain.San Francisco is amazing in September with as little as 3 rainy days on average, so plan adventures in the great outdoors.
Here’s how September is compared with other months in the amount of precipitation, total mm:
San Francisco wettest month is December, where a typical day has a 39% chance of precipitation and 117 mm of rainfall per day. July, on the other hand, is the driest month with a mere 0% chance of precipitation and 0 mm of rainfall per day.
How was the weather last September in San Francisco?
This is the weather in San Francisco in September 2023:
1 September
☁️
+69°F
2 September
☁️
+72°F
3 September
☁️
+71°F
4 September
☁️
+71°F
5 September
☁️
+75°F
6 September
☁️
+73°F
7 September
☁️
+70°F
8 September
☀️
+76°F
9 September
☀️
+73°F
10 September
☀️
+72°F
11 September
☀️
+76°F
12 September
☁️
+73°F
13 September
☀️
+73°F
14 September
☁️
+72°F
15 September
☁️
+69°F
16 September
☁️
+68°F
17 September
☁️
+70°F
18 September
☀️
+71°F
19 September
☁️
+69°F
20 September
☁️
+69°F
21 September
☀️
+70°F
22 September
☀️
+70°F
23 September
☁️
+68°F
24 September
☁️
+69°F
25 September
☁️
+74°F
26 September
☀️
+73°F
27 September
☀️
+74°F
28 September
☀️
+76°F
29 September
☀️
+73°F
30 September
☁️
+68°F
In September 2023 San Francisco had 12 sunny days, 18 cloudy days, and 0 rainy days. The average maximum temperature was +72°F, with an absolute maximum of +77°F and a minimum of +68°F. The average humidity was 84%, with a maximum of 100% and a minimum of 60%. The average wind speed was 1 m/s, with a maximum of 7 m/s and a minimum of 0 m/s.
Are you planning a trip in September?
Climate Change Over the Years
This is how San Francisco climate has changed over the last 43 years.
The climate in San Francisco in September has not changed that much over the last 43 years.
The average temperature was the lowest in 1982 (+65°F) and the highest in 2014 (+70°F). The driest year was 2013 with only 127 mm of rainfall, and the wettest year was 1983 with 1162 mm.
FAQ
Frequently asked questions about the weather in San Francisco in September:
Is September a good time to visit San Francisco?
September is a really good time to go to San Francisco. The weather is nice so plan your packing around outdoor activities and exploring. Check out other good time to visit San Francisco.
Can you sunbathe in San Francisco in September?
September is warm in San Francisco. You may enjoy some beach or pool time in the day, but pack something a tad warmer for the evening.
Can you swim in San Francisco in September?
Swimming in San Francisco in September is challenging and not recommended for inexperienced swimmers or without proper equipment and preparation.
Is San Francisco rainy in September?
San Francisco is usually dry in September. Plan your packing around outdoor activities and exploring.
Is it sunny in San Francisco in September?
Usually, it’s not very sunny in San Francisco in September, often it’s pretty cloudy. Pack for any eventuality; layering can help reduce the number of bulky items needed.
For this page, we’ve looked at the typical weather in San Francisco, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.
